Hi,

It's hard for us to tell you what are good threads or not with out seeing what you are seeing.
Welding in a replacement bung or getting a Heli-coil insert is just about what you are looking for.
It's a spark plug thread and are readily available.

In the case of the sensor you do not need full depth threads because you are not requiring them to hold their full tensional strength. In other words the sensor is not under the pressure of cylinder compressions.
As long as it "holds tight" enough not to rattle loose and the outside air cannot be sucked past the sensors seating shoulder it should be ok.
Eventually carbon deposits with make it somewhat tighter.
Under normal installations the use of an anti-seize paste is advised to prevent the reasons why if left in too long it tears some thread out.
I do not know of a set recommendation of how often the paste should be replenished but good maintenance might be every 25,000 miles.
Heat and burning hydrocarbons accelerates oxidation which is the process of combustion to begin with.
The dissimilar metals in the paste help break up some of the chain reactions going on for a time.
It's also recommended to protect the spark plug threads in the aluminum head of our engines.
It's like "Brylcream" hair dressing, "A little dab will do ya!" Just got to figure out, what's a "Dab?"
A Hint is ... it must be less than a "Dollop" of Sour Cream.

Ultimately it's your call to keep an eye on it to see if it's staying tight. You might want to put a spot of paint on one side, so that you can see easily, to see if it rotates any for a while.

Phil